Question

Molecularity of a reaction can be:

• A. Zero
• B. \(-2\)
• C. 1
• D. 0.5

Hint:

For molecularity:
- Applies to elementary reactions only.
- Must be a positive integer (1, 2, 3, etc.).
- Distinguish from reaction order, which can be fractional or zero.

Answer 1

The Correct Option is C

Molecularity is the number of molecules or ions colliding in an elementary step of a reaction. It is always a positive integer (1, 2, 3, etc.) for elementary reactions.
Step 1: Analyze options
- (A) Zero: Molecularity cannot be zero, as at least one species must participate in an elementary step.
- (B) \(-2\): Molecularity cannot be negative, as it represents a count of colliding species.
- (C) 1: Unimolecular reactions (e.g., radioactive decay, \(\mathrm{A} \rightarrow \text{products}\)) have molecularity 1.
- (D) 0.5: Molecularity cannot be fractional, as it is a whole number.
Step 2: Conclusion
Molecularity can be 1 (unimolecular), matching option (C).